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by ydant
5823 days ago
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It's an interesting project. I grabbed it and wrote a quick Flickr FS. It seems that it's a little limited for really laggy webservices in that you specify the type of an entry (directory, folder) by the type of data you return, and it calls the same method for readdir, getattr, and read, with no way to differentiate in your code. In order to specify the type of an entry, you have to return the data for that entry. So a sub-folder has to return an array. There's no way to differentiate between, say, an ls on the parent folder or on the sub folder (e.g. ls / and ls /foo both return the method mapped to /foo), so you have to query all of the subfolders' contents at once AND cache it so it doesn't have to be re-queried when the user wants to look at the sub-folder. Hopefully I'm overlooking something, but the source is pretty straightforward. The good part is it'd be easy to modify to ask for types separately. Actually just passing in another argument indicating what mode it's in would help. |
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My target application was things like automounters, or the low-latency database querying sort of thing I mention in the actual blog post. Since I wanted to be able to have the filesystem structure change as it was accessed, I decided to make any sort of caching entirely an application-layer problem, not a RouteFS-layer problem.
I think it would be possible to extend RouteFS to handle this sort of case more gracefully. One option in particular might be to take advantage of python-fuse's stateful I/O feature (which lets you associate a Python object with open file descriptors in your filesystem [1]) so that reads from the same file don't result in the same lookup over and over again, although this certainly doesn't help for directories.
But in any case, I'd certainly love to see ideas for extending RouteFS to make it easier to make it more performant. Submissions in the form of patches are always excellent, but even suggestions for API changes would be welcome - feel free to open an issue on Github either way (http://github.com/ebroder/python-routefs/issues).
[1] See "Filehandles can be objects if you want" in http://fuse.cvs.sourceforge.net/viewvc/fuse/python/README.ne... for more information